JPH107413A - Production of highly pure carbon monoxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for pyrolyzing formic acid to produce carbon monoxide, capable of producing the highly pure carbon monoxide by using a zeolite catalyst preliminarily modified with a mineral acid and pyrolyzing the formic acid at 110-150 deg.C. SOLUTION: This method for producing carbon monoxide comprises catalytically pyrolyzing formic acid in the presence of a zeolite catalyst. Therein, a zeolite preliminarily modified with a mineral acid is used. Since the reaction proceeds at a low reaction temperature in high selectivity, highly pure carbon monoxide low in the contents of hydrogen and methane can profitably be obtained. When H-mordenite and H-ZSM-5 are used as catalysts in the method of the invention, the reaction can be continued in high conversion and in high selectivity over two months or longer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing high-purity carbon monoxide. More specifically, the present invention relates to a method for producing high-purity carbon monoxide having a purity of 99.99% or more used in the field of producing semiconductors such as integrated circuits.

[0002]

2. Description of the Related Art Conventionally, as a method for producing high-purity carbon monoxide, natural gas is subjected to steam reforming to generate high-concentration carbon monoxide, which is further separated and purified, or formic acid is converted to sulfuric acid or a solid catalyst. There is known a method of decomposing, dehydrating and purifying by using a method. Considering the purification process, the formic acid decomposition method is advantageous because carbon monoxide can be obtained with a high selectivity, but when dehydration reaction is performed using sulfuric acid, the water generated in the reaction reduces the sulfuric acid concentration. In addition, a large amount of sulfuric acid is required to maintain the reaction rate, and it is not industrially preferable from the viewpoint of treating wastewater containing sulfuric acid. On the other hand, the method of decomposing formic acid using a solid catalyst does not have the above-mentioned problem, but causes a side reaction of producing hydrogen and carbon dioxide in addition to the reaction of producing carbon monoxide.

[0003] Catalysts which can be used in the method using a solid catalyst include ion exchange resins, alumina, alumina / phosphor pentoxide, calcium phosphate, calcium borophosphate, clinoptilolite, H-ZSM-5 / alumina and the like. It has been known.

However, the usable temperature of the ion exchange resin is limited to about 100 to 130 ° C., and the conversion of formic acid at this temperature is not high. Alumina has a high conversion at 300 ° C. or higher, but the selectivity of carbon monoxide is 99.
Since it is less than 7%, a considerable amount of hydrogen is contained as an impurity. Alumina / phosphorus pentoxide, calcium phosphate, calcium borophosphate and clinoptilolite show the same tendency as in the case of alumina. On the other hand, H-ZSM-5 / alumina has a conversion of 99.5% and a selectivity of 10 at a reaction temperature of 250 ° C.
It is reported that carbon monoxide is given at 0% and no hydrogen is generated (Bull. Soc. Belg., 92, 225 (1983)). However, according to the additional test by the present inventors, in the long-run test of the H-ZSM-5 / alumina catalyst, 0.5 vol% of hydrogen is generated at the reaction temperature of 250 ° C. from the beginning of the reaction. Therefore, H-
ZSM-5 / alumina is also not a good catalyst for producing high-purity carbon monoxide.

As described above, it is difficult to simultaneously achieve high conversion and high selectivity with any of the catalysts.
Another problem is that the production capacity of carbon monoxide per unit volume of the catalyst is low. Further, the H-ZSM-5 / alumina catalyst is almost satisfactory in terms of the conversion, but the selectivity decreases over time, so that it is difficult to say that it is an industrially preferable catalyst. Therefore, the present inventors, in order to develop a method for efficiently and industrially obtaining high-purity carbon monoxide,
We searched for a method to decompose formic acid into carbon monoxide and water with high conversion and high selectivity. As a result, they have found a method of reacting by adding a mineral acid together with formic acid using a zeolite-based catalyst (JP-A-7-33421). However, in this method, the temperature at which the decomposition activity of formic acid is sufficiently exhibited is 200 ° C.
As described above, it was confirmed that methane was generated at this temperature in addition to hydrogen and carbon dioxide. Since methane is difficult to remove by an ordinary purification method, it is desired to lower the reaction temperature to suppress the generation of by-products such as methane.

[0006]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide satisfactory results in both the reaction rate and the selectivity of the reaction even at a low temperature and to suppress the generation of by-products such as hydrogen and methane. It is an object of the present invention to provide a method for producing high-purity carbon monoxide which can be performed.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve such a problem, and as a result, when a thermal decomposition reaction of formic acid is carried out using a zeolite catalyst previously modified with a mineral acid,
The present inventors have found that sufficient results can be obtained in both the reaction rate and the selectivity of the reaction even at a relatively low temperature, and that the production of hydrogen and methane can be suppressed, thus completing the present invention.

That is, the gist of the present invention is to provide (1) a method for producing carbon monoxide by thermally decomposing formic acid by using a zeolite-based catalyst which has been modified with a mineral acid in advance;
A method for producing high-purity carbon monoxide, wherein a thermal decomposition reaction of formic acid is carried out at 0 ° C .; (2) the production method according to (1), wherein the zeolite-based catalyst is H-mordenite or H-ZSM-5; (3) The method according to (1) or (2), wherein the mineral acid is sulfuric acid, (4) The method according to any one of (1) to (3), wherein the concentration of the mineral acid is 30 to 98% by weight. The method (5) wherein the zeolite-based catalyst is modified with a mineral acid by immersing it in a 30-98% by weight aqueous solution of a mineral acid at 20-50 ° C for 0.5-24 hours. (4) The production method according to any of (1) to (6), wherein the modification of the zeolite-based catalyst with a mineral acid fills a column filled with the zeolite-based catalyst with a 30 to 98% by weight aqueous solution of a mineral acid, and sets the column at 0.2 to 50 ° C. After leaving for 5 to 24 hours, the mineral acid aqueous solution flows out The method of manufacturing a is (1) to (4) according to any one performed by a method in which,
About.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below.

The zeolite-based catalyst used in the present invention includes H-mordenite, H-ZSM-5, clinoptilolite, etc. Among them, H-mordenite and H-ZSM-5 are excellent in acid resistance. Therefore, the catalyst is suitable for the purpose of the present invention. As these zeolite-based catalysts, commercially available products can be used as they are.
As the H-mordenite catalyst used in the present invention, Si / Al
There is no particular limitation as long as the atomic ratio is about 5 to about 30, and both natural mordenite and synthetic mordenite can be used. For example, the atomic ratio of Si / Al is about 5 for natural products and about 5 to about 30 for synthetic products, and any ratio can be used as a catalyst. If the Si / Al atomic ratio is less than about 5,
Since the catalyst activity tends to decrease, it is not preferable. If it is larger than about 30, catalyst preparation tends to be complicated and economically disadvantageous.

[0011] H-mordenite is usually 1 part of mordenite.
It is obtained by treating with a specified amount of hydrochloric acid. H-mordenite itself has the activity of decomposing formic acid, but a high temperature of 200 ° C. or higher is required for the activity to be sufficiently exhibited. In the present invention, by modifying H-mordenite with a high concentration of a mineral acid, sufficient results are obtained in both the reaction rate and the selectivity of the reaction even at a relatively low temperature, and the production of hydrogen and methane is suppressed. It has been found for the first time that the effects of the present invention are achieved. Although the mechanism is not clear, it is assumed that the catalytic action of zeolite modified with a high concentration of mineral acid and the dehydration reaction by mineral acid on the catalyst surface act synergistically to exert the effect of the present invention. Seem.

As the mineral acid which can be used in the present invention, sulfuric acid, hydrochloric acid, phosphoric acid and the like can be mentioned. Among them, sulfuric acid can be preferably used from the viewpoint of cost and ease of wastewater treatment. The concentration of the mineral acid is not particularly limited, but the treatment may be usually performed at 30 to 98% by weight, preferably 50 to 80% by weight. If the concentration of the mineral acid is lower than 30% by weight, the activity of forming carbon monoxide is low, and it is difficult to achieve the object of the present invention.

In the present invention, as a method of modifying the zeolite-based catalyst with a mineral acid in advance, for example, prior to using the zeolite-based catalyst, 30-98% by weight sulfuric acid or an aqueous sulfuric acid solution at 20-50 ° C. Immersion method for 5 to 24 hours, or 30 to a column filled with a zeolite catalyst.
A method of filling with an aqueous solution of sulfuric acid of about 98% by weight, leaving the mixture at 20 to 50 ° C. for 0.5 to 24 hours, and then flowing out the aqueous solution of sulfuric acid. When hydrochloric acid or phosphoric acid is used as the mineral acid, 10 to 37% by weight of hydrochloric acid or 30 to 98% by weight of phosphoric acid can be used instead of the above sulfuric acid.

As the formic acid used in the present invention, a commercial product (for example, manufactured by Koei Co., Ltd.) can be used as it is. The concentration of formic acid at the time of use is not particularly limited, but if 40 to 100% by weight of formic acid or an aqueous solution of formic acid is used, the reaction can be carried out efficiently. Concentration 40
When the amount is less than% by weight, the remaining portion other than formic acid is water, so that a large amount of energy is required for heating.

The reaction in the present invention is carried out by bringing vaporized formic acid into contact with a catalyst previously modified with a mineral acid as described above, followed by thermal decomposition. As the reactor, a reaction vessel or a tower filled with a catalyst is used. Charge the catalyst and formic acid into the reactor,
Although carbon monoxide may be generated by heating,
In consideration of reaction efficiency, it is preferable to pass formic acid vapor through the column packed with the catalyst. In this case, formic acid may be passed through a single-column reactor, or a multitubular reactor may be used.
In particular, in a multi-tube reactor, one-sided flow of gas can be prevented,
Further, a heat transfer area for heating can be secured, which is preferable.

The reaction using the present catalyst proceeds at a relatively low temperature,
The reaction temperature is usually 110-150 ° C., preferably 120
１５０150 ° C. When the reaction temperature is lower than 110 ° C., the reaction becomes difficult to proceed, and the conversion becomes low, which is not preferable. When it exceeds 150 ° C., a side reaction occurs, and the hydrogen and methane concentrations in carbon monoxide tend to increase. Absent.

The material of the reactor used in the present invention is required to be one which is not corroded by formic acid and carbon monoxide and does not affect the reaction. Materials can be suitably used. In addition, since the reaction proceeds at a relatively low temperature of 110 to 150 ° C., it is possible to use equipment using glass lining.

The carbon monoxide obtained by this reaction contains water and trace amounts of hydrogen, carbon dioxide and methane as impurities. As a method for obtaining high-purity carbon monoxide by further adding a purification step to this gas, a combination of known methods can be used. As an example,
After removing trace amounts of unreacted formic acid and carbon dioxide by washing with a thin sodium hydroxide solution, drying and removing water to obtain high-purity carbon monoxide. The purity of carbon monoxide obtained in this way is 99.99% or more, and it can be used not only in the semiconductor manufacturing field but also for various uses.

[0019]

The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited by the examples and the like shown here.

Example 1 A column having an inner diameter of 2.5 cm and a length of 60 cm was filled with H-mordenite (Si / Al atomic ratio: 7.6) to a length of 11 cm. The catalyst used is 50 ml. 7
A 0% by weight sulfuric acid solution was filled and contacted with the catalyst at 40 ° C. for about 2 hours. After allowing sulfuric acid to flow out of the column,
An 88% by weight aqueous solution of formic acid was fed into the upper part of the reactor at a rate of 45 g / h as a vapor at 130 ° C. through a vaporizer provided in the preceding stage of the column. The reaction is carried out by heating the outside 13
Performed at 0 ° C.

The reaction gas was taken out from the lower part of the reactor and analyzed, and the conversion and selectivity of the reaction were determined. The conversion of formic acid was determined by quantifying unreacted formic acid, and the selectivity to carbon monoxide was determined by quantifying the amount of generated hydrogen with a gas chromatograph mass spectrometer (GC-MS). As a result, the reaction proceeded with a conversion of formic acid of 99.9% and a selectivity to carbon monoxide of 99.99% or more.

The obtained reaction gas was washed with a 10% aqueous sodium hydroxide solution to remove a trace amount of carbon dioxide, and further washed with water. The gas was dried over zeolite. As a result, high purity carbon monoxide of 99.99% or more was obtained. This gas contains 0.2p of hydrogen as an impurity.
pm and 0.4 ppm of methane.

Example 2 A reaction was conducted in the same manner as in Example 1 except that an aqueous solution of 70% by weight of formic acid was used as a raw material instead of the aqueous solution of formic acid of 88% by weight. As a result, the reaction proceeded with a conversion of formic acid of 99.9% and a selectivity to carbon monoxide of 99.99% or more. As a result of performing purification treatment in the same manner as in Example 1, 99.99%
The above high-purity carbon monoxide was obtained, and contained 0.2 ppm of hydrogen and 0.4 ppm of methane.

Example 3 A reaction was carried out in the same manner as in Example 2 except that the reaction temperature was changed to 150 ° C. As a result, the reaction proceeded with a conversion of formic acid of 99.9% and a selectivity to carbon monoxide of 99.99% or more. As a result of performing purification treatment in the same manner as in Example 1, 99.
High-purity carbon monoxide of 99% or more was obtained, and contained 0.2 ppm of hydrogen and 0.4 ppm of methane.

Example 4 The same procedure as in Example 1 was carried out except that H-ZSM-5 was used as a catalyst. As a result, the reaction proceeded with a conversion of formic acid of 99.9% and a selectivity to carbon monoxide of 99.99% or more. As a result of performing purification treatment in the same manner as in Example 1, 99.
High-purity carbon monoxide of 99% or more was obtained, and contained 0.3 ppm of hydrogen and 0.5 ppm of methane.

Example 5 Following Example 1, the reaction was continued under the same conditions for 70 days (1680 hours). After 70 days, the conversion of formic acid is 99.9%,
The selectivity to carbon monoxide was 99.99%, and no particular deterioration of the catalyst over time was observed. As a result of performing the purification treatment in the same manner as in Example 1, 99.99% or more of high-purity carbon monoxide was continuously obtained, in which hydrogen contained 0.2%.
ppm and methane were contained in 0.4 ppm.

Comparative Example 1 A column having an inner diameter of 2.5 cm and a length of 60 cm was filled with H-mordenite (Si / Al atomic ratio: 7.6) to a length of 11 cm. The catalyst used is 50 ml. Then, 88% by weight
Of formic acid aqueous solution was fed into the upper part of the reactor at a rate of 45 g / h as a vapor at 130 ° C. through a vaporizer provided in the preceding stage of the column. The reaction was performed at 130 ° C. by heating the outside. Take out the reaction gas from the lower part of the reactor and analyze it,
The conversion and selectivity of the reaction were determined. The conversion of formic acid was determined by quantifying unreacted formic acid, and the selectivity to carbon monoxide was determined by quantifying the amount of generated hydrogen with a gas chromatograph mass spectrometer (GC-MS). As a result, the conversion of formic acid was 10% and the selectivity to carbon monoxide was 99.99%.
The reaction proceeded at 99% or more. The obtained reaction gas is 1
The resultant was washed with a 0% aqueous sodium hydroxide solution to remove trace amounts of carbon dioxide, and further washed with water. The gas was dried over zeolite. As a result, high purity carbon monoxide of 99.99% or more was obtained. This gas contained 5 ppm of hydrogen and 2 ppm of methane as impurities.

Comparative Example 2 A column having an inner diameter of 2.5 cm and a length of 60 cm was filled with H-mordenite (Si / Al atomic ratio: 7.6) to a length of 11 cm. The catalyst used is 50 ml. Then, 96% by weight
0.5% by weight of sulfuric acid in 88% by weight of formic acid aqueous solution
The added product was sent to the upper part of the reactor at a rate of 45 g / h as vapor at 130 ° C. through a vaporizer provided in the preceding stage of the column. The reaction was carried out at 250 ° C. by heating the outside. The reaction gas was taken out from the lower part of the reactor and analyzed, and as a result, the reaction was proceeding at a conversion of formic acid of 99.9% and a selectivity to carbon monoxide of 99.99% or more. The obtained reaction gas was washed with a 10% aqueous solution of caustic soda to remove a trace amount of carbon dioxide, and further washed with water. The gas was dried over zeolite. As a result, high purity carbon monoxide of 99.99% or more was obtained. This gas contains 1.6 ppm of hydrogen and 1.2 ppm of methane as impurities.
Was included.

Comparative Example 3 The procedure was as in Example 1, except that the reaction temperature was 225 ° C. As a result, the reaction proceeded at a conversion of formic acid of 99% and a selectivity to carbon monoxide of 99.99% or more. Example 1
As a result of performing the purification treatment in the same manner as described above, high-purity carbon monoxide having a purity of 99.99% or more was obtained.
pm and 5 ppm of methane.

[0030]

According to the present invention, when formic acid is catalytically decomposed with a zeolite-based catalyst to obtain carbon monoxide, the reaction is carried out using a zeolite-based catalyst which has been modified with a mineral acid in advance, thereby achieving a low reaction temperature and a high selectivity. Therefore, high-purity carbon monoxide having a low content of hydrogen or methane can be industrially advantageously obtained. When H-mordenite and H-ZSM-5 are used as catalysts in the method of the present invention, the reaction can be continued while maintaining high conversion and high selectivity over a period of two months or more.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Manabu Enomoto 346-1 Miyanishi, Harima-cho, Kako-gun, Hyogo Pref.

Claims (6)

[Claims] 1. A method for producing carbon monoxide by thermally decomposing formic acid, wherein a thermal decomposition reaction of formic acid is carried out at 110 to 150 ° C. using a zeolite catalyst modified in advance with a mineral acid. A method for producing pure carbon monoxide. 2. The method according to claim 1, wherein the zeolite catalyst is H-mordenite or H-ZSM-5. 3. The method according to claim 1, wherein the mineral acid is sulfuric acid.
The manufacturing method as described. 4. The production method according to claim 1, wherein the concentration of the mineral acid is 30 to 98% by weight. 5. The method for modifying a zeolite-based catalyst with a mineral acid is as follows:
0.5 to 0.5% in a 30 to 98% by weight aqueous solution of mineral acid at 0 to 50 ° C.
The method according to any one of claims 1 to 4, which is performed by a method of immersion for up to 24 hours. 6. A method of modifying a zeolite-based catalyst with a mineral acid, filling a column filled with the zeolite-based catalyst with a 30 to 98% by weight aqueous solution of a mineral acid, leaving the column at 20 to 50 ° C. for 0.5 to 24 hours, and then adding the mineral acid to the column. The method according to any one of claims 1 to 4, wherein the method is carried out by flowing out an aqueous solution.